Associate Fellow and University of Colorado Assistant Professor Ann-Marie Madigan began the journey that led her to a career in theoretical astrophysics when she walked into her first physics class in an all-girls convent school at age 16. There she discovered a deceptively simple question written on the blackboard: What is Light? She thought the question was absolutely fascinating. From that day forward, she wanted to go to college and learn about physics.
Madigan went to college at the National University of Ireland, Galway. In 2004, she graduated with honors with a major in Physics & Astronomy. She wasn’t sure yet what she wanted to do with her life, but she knew she wanted to learn more about physics. So she went backpacking in India for a year, which was a wonderful experience.
While she was in India, Madigan applied to several programs offering research Master’s degrees. She wanted to get some research experience before applying to a Ph.D. program. Enticed by an artistic website on cosmology, she applied and was accepted to Leiden University in the Netherlands.
There she met Professor Yuri Levin and postdoc Clovis Hopman. The two researchers jointly advised both her Master’s and Doctoral work. Levin won her admiration via his class in general relativity in which he derived everything from first principles. Madigan discovered she could do the math and actually derive white holes and space-time diagrams. For his part, Hopman introduced her to stellar-sized black holes, neutron stars, white dwarfs, and supermassive black holes. Madigan arranged to work with both of them.
The three became a research team. For her Ph.D. research, Madigan won a NWO Top Talent award that provided funding for her to investigate the stars and gas swirling around a black hole. Because of the award, she was able to design her own Ph.D. research program, which is quite rare. Her thesis reported the results of her theoretical astrophysics work on the Secular Stellar Dynamics near Massive Black Holes.
After earning her Ph.D. from Leiden University, Madigan won a NASA Einstein Postdoctoral Fellowship that she used to continue her theoretical astrophysics work at the University of California at Berkeley. Her postdoc proved challenging since there were no faculty in theoretical astrophysics working on topics she wanted to pursue. So once again, Madigan designed her own research program. For the last two years of her four-year postdoc at Berkeley, Madigan worked with graduate student Mike McCourt and postdoc Ryan O’Leary to delve more deeply into gas dynamics around black holes.
Madigan also expanded her research to include planetary dynamics because the disks of stars around black holes share some similar characteristics with disks of planets around stars.
Madigan discovered that the bizarre dynamics exhibited by stars in a thin disk in eccentric orbits look a lot like what she thinks may happen to the minor planets in the outer solar system. Her work on the solar system suggests that this gravitational instability occurs because the minor planets gravitationally perturb each other.
Soon after she published a new theory explaining this behavior, another group published a paper hypothesizing the existence of Planet Nine, a new large planet in the outer solar system. Suddenly Madigan’s theory and the Planet Nine theory were competing theories to explain the behaviors of dwarf planets in the outer solar system.
Madigan spends about half her time investigating the NOT PLANET NINE theory. She has a graduate student working on putting this theory in the context of the solar system that also has Jupiter, Saturn, and Neptune scattering everything. The goal is to predict the location and mass of the solar system’s minor planets; this population could form a new structure in the outer solar system, ten times more massive than the Kuiper Belt.
The second half of Madigan’s research focuses on disks of stars around black holes in highly elliptical orbits that are clustered together on one side of the disk. This is exactly how a huge number of stars are distributed around the supermassive black hole at the center of our neighboring galaxy Andromeda. Madigan is investigating the dynamics of stars born into this system.
She’s interested in understanding how often the stars get sucked into the black hole. This process, known as a tidal disruption, happens when the gravity exerted by the black hole on one side of the star overcomes the forces that bind the star together, literally ripping the star apart. Such a tidal disruption produces a luminous event around the black hole that we can see with telescopes on Earth.
In her spare time, Madigan enjoys studying geology and hiking through national parks.